1. Field of the Invention
The present invention relates generally to automotive fastener assemblies, and more specifically to fastener assemblies for securing plastic finish panels to metallic substrates.
2. Description of the Related Art
As part of the overall effort of automotive manufacturers to improve fuel economy of automotive vehicles, plastic finish panels have come into widespread use; even broader use is planned for the future. Most of the uses of plastic finish panels in the automotive vehicle arts require that a plastic sheet or panel be secured to an underlying metallic substrate through suitable fasteners. As in most mechanical joining applications, one of the primary fastening systems of choice is the use of a threaded fastener spanning the two components to be secured together and exerting a clamping load between them. In the target application for the automotive industry, the mounting of a plastic body panel on a metallic substrate such as a frame or underbody, certain impediments to the presentation of a finish panel of good quality and appearance have been experienced. The significant difference in coefficient of thermal expansion between the plastic panel and the metallic substrate tends to result in displacement between these two components, and when a fastener is arranged to hold the panel fast with respect to the substrate, distortion can result.
The automotive industry has addressed this problem by providing fastener mechanisms which permit some relative movement between the panel and the substrate. U.S. Pat. No. 5,098,765 to Bien is exemplary of solutions suggested in the industry, providing mounting blocks engageable in the substrate to permit fore and aft movement which mounts a fastener receiving plate through agency of laterally extending wings. This and other solutions have been found to be disadvantageously complex and expensive to produce and also fail to directly provide for movement of a fastener receiving device or nut in response to thermal growth of the plastic panel. This direct compensation for thermal growth is, at least in some applications, the most reliable way to provide for the desired compensating movement.